30fps to 24fps?

[Cracker Funk]

The audio guy only needs to know this stuff for syncing purposes. And they won't be syncing to the raw footage, but to the edited movie. So, all is well.

And I never said there is no difference. I'm just saying, quite factually, that nobody can tell the difference. Did you watch the video I posted? Can you tell the difference?

And no, there is no pulldown involved here. Pulldown is when you add frames. This is the opposite. Call it a "pullup". Every fifth frame will be ignored, and nobody will notice.

For all intents and purposes -- there is no difference, just do it. I do it all the damn time.

[jax_rox]

Hmm...
I ain't no professional editor so I can't comment anymore than I already have.

I'm also not really sure why you'd be syncing your audio after your picture lock. How would one sync the audio after the clapperboard and clap have been stripped out of the edit..?

[Cracker Funk]

Originally Posted by jax_rox

Hmm...
I ain't no professional editor so I can't comment anymore than I already have.

I'm also not really sure why you'd be syncing your audio after your picture lock. How would one sync the audio after the clapperboard and clap have been stripped out of the edit..?

That's a valid question. Though, it's a question that would only be asked by someone who doesn't edit.

For audio purposes, the slate is a few decades out-of-date. Nobody syncs to the slate anymore. In a thread not long ago, I openly questioned why the heck we even use the slate. I got some good answers, and all of them had to do with visual organization. There's rarely a need for that CLAP.

This is all assuming that we're talking about video (which is what pretty much everyone on this website shoots on). I suppose actual film is different, but for video, there is scratch audio, recorded with video. Syncing external audio is easy as pie.

If you've got an audio guy, you can rest assured he will not be editing audio in FCP or Premiere. You will deliver him a locked edit, and all the audio files, and they will go to town, using their own preferred audio editing software. They won't need the slate.

[jax_rox]

Yeah, I've sat in on audio sessions on Pro Tools stages...

I suppose I've worked quite a lot in actual film or Red/Alexa, rather than video in general so I suppose my questions and viewpoint originate from that point of view - we always slate everything, but then there's no scratch track on film, and the workflow to get a scratch track into Red or Alexa is hardly anything easy

[AudioPostExpert]

This is quite a complex issue. When working with physical frames, say with 35mm film, frame rates are extremely important and mixing frame rates is going to become an audio nightmare unless it is very carefully planned in advance of filming and the production sound mixer and audio post team really know what they are doing, as it involves carefully manipulating the sample frequency of the audio both during filming and in post.

Working purely in digital for capture, editing and output can make life easier, in a sense, because converting between frame rates can be done with interpolation, rather than speeding up or slowing down fixed physical frames. However, there are numerous dangers with this workflow too. How exactly is the software interpolating, is it just interpolating the images or is it also interpolating the linked sound? If it's the latter, you're likely to run into a bunch of hurt. If it's just the image then the only worries are visual artefacts and any slight timing changes, which could easily affect audio sync.

Very recently I had a 1080p short film delivered to me for audio post and it had been rendered at 24fps by mistake, instead of at the original and delivery frame rate of 23.976fps. This caused all kinds of audio problems and was very difficult to diagnose because of course both these frame rates have 24 frames in a second of time-code. Had this problem not been detected, there's a pretty good chance that by the end of a 5 minute short, even with this very tiny difference in frame rates, the audio would have been out of sync with the picture by about 7 frames.

There are several different workflows to how we sync sound to picture, the best is from time-code embedded in the audio files during filming but this requires the recorder to be time-code sync'ed with the camera/s during filming. Our preliminary guide is from the work of the picture editor but this usually need adjustment as the editor does not have the equipment to accurately sync sound and picture. It's a big subject area to get into in a short post, so I won't! But just to say; if you can, always film with camera/recorder time-code locked and always slate, as the more info we have the better. I gave some info on workflow and materials exchange between picture editor and audio post here: http://www.indietalk.com/showthread.php?t=41292

Bottom line is that changing or mixing frame rates is fraught with dangers, especially if handing off the sound to an audio post guy. You might be lucky and get away with it, depending on what your software does and how you use it but as a general rule, avoid it like the plague. As a cautionary tale, I was once involved in a professional project which ended up going bankrupt and never got finished because of frame rate issues. I've heard similar tales from others.

G

[jax_rox]

We always slate everything, and most editors I know of sync audio with picture before actually getting into editing.

If nothing else, then I'm sure the Director would like to see the edit come together with decent audio, rather than with scratch-track stuff that often times is barely audible... not to mention the issues I can imagine that would arise in the pacing of the editing when you can barely hear what someone's saying.
And considering that DSLRs can't be timecode-linked, that timecode often slips if it's not constantly re-checked, and the fact that timecode jam-slates are hugely expensive, I can't imagine timecode would be a reliable way to sync on most low-budget shows. Therefore, what does the sound editor use to sync audio if they have only a picture lock edit and the raw sound files? I can't see how that would work at all, not to mention the fact that unless you provide them with an extensive list of what take was used where, it would create issues in syncing as an editor may have had to wade through 10 takes to find the one used...

Just seems like a lot more work that you'd be paying for, that you could have your editor or assistant editor spend a day or two on before he starts editing and save a lot of hassles and issues and time down the line...

But then, I'm a DP not an editor or sound guy.

[Cracker Funk]

Seriously, you guys are making a big deal out of nothing. Also, you're speaking in generalities, none of which apply to the specific subject at hand. You're also speaking authoritatively about a subject in which you are no authority.

Originally Posted by AudioPostExpert

Very recently I had a 1080p short film delivered to me for audio post and it had been rendered at 24fps by mistake, instead of at the original and delivery frame rate of 23.976fps.

Yeah, that was me. Sorry about that. I was using an export setting I'd never used before, and I missed that little important detail.

But that actually has NOTHING to do with what we're talking about. For the project you're describing, all that matters is the frame rate that is exported to. In the example you reference, I mistakenly exported to true 24p, instead of 23.98, and that caused headaches. The frame rate of the raw footage, however, would have absolutely NO bearing on your audio edit. No matter how much of my footage might have been 24/30/60, the final output would be the same.

Even if the OP were recording time-coded audio (I doubt it), there still would be zero issue in mixing frame rates, during the edit. Let's say all of the audio is time-coded for 24. The DP goofs and shoots some footage at 30. Uh-oh, now that mistake video and the audio have different time codes. What are we to do? The sky is falling!

Oh, wait. We can edit all of the video in a 24fps timeline, export to 24 and vioala -- now the old 30fps footage is time-stamped with 24fps time code. Doesn't help if you're syncing to the slate, but how many people on this forum are doing that? For most people on this forum, the scratch audio is all you need, and the slate gets practically no use.

All is well. The sky is not falling. Just edit the damn movie, no luck required to get the job done.

[TheArtist]

I sync to scratch and sometimes I feel like a slate would make it easier. But maybe my technique is crappy.

[AudioPostExpert]

Originally Posted by jax_rox

Therefore, what does the sound editor use to sync audio if they have only a picture lock edit and the raw sound files? I can't see how that would work at all, not to mention the fact that unless you provide them with an extensive list of what take was used where, it would create issues in syncing as an editor may have had to wade through 10 takes to find the one used...

Just seems like a lot more work that you'd be paying for, that you could have your editor or assistant editor spend a day or two on before he starts editing and save a lot of hassles and issues and time down the line...

Obviously the dialogue editor needs more than just a locked edit and the raw sound files. We need at least a scratch-track (with sync'ed camera sound). On the face of it, I agree it appears to be quicker/cheaper to have the assistant pic editor cut in the better mic's and in practice, on higher budget shows this is what happens but in reality this actually means paying for this job to be done twice. The problem is that a picture editor (or assistant) does not have the equipment to either accurately sync the sound or to accurately decide which mic is best. In reality, virtually all the scenes you hear in a finished professional film are a combination of various takes, many of which are unrelated to the take used in the visuals, plus of course the odd bit of ADR thrown in when nothing else usable can be found.

I agree, there's no point in recording time-code unless you can sync-lock the recorder and camera together and this is maybe too expensive for those with low budgets. On the other hand, not paying for this probably a false economy because you'll likely pay even more at the other end, during post. With a full length feature it's going to take months to find and go through all the alt takes (and mic's) amongst the thousands of files and this is also going to cost a fortune. The only other alternative is ADR, which is both costly and degrades the quality of the final product.

Originally Posted by Cracker Funk

The frame rate of the raw footage, however, would have absolutely NO bearing on your audio edit. No matter how much of my footage might have been 24/30/60, the final output would be the same.

I'm afraid this is inaccurate, or at least, it is not always accurate. Fractional frame rates, like 23.976fps (or NTSC, 29.97fps) are actually 24fps (or 30fps in the case of NTSC) played slightly slow. One second of time-code with these frame rates does not equal one second of real time, which is why DF (drop frame) rates had to be invented. If you film at 23.976fps (and record audio at this rate) and then do a straight conversion from 23.976fps to 24fps then the picture will slightly speed up relative to the original audio and they will gradually drift out of sync with each other. The way around this is to convert using interpolation but then the issues I listed in my previous post apply. This is true when converting any frame rate to any other frame rate. In fact there is/was a very common workflow which involves this very problem, which is why "pull up" and "pull down" audio recording rates exist.

Originally Posted by Cracker Funk

You're also speaking authoritatively about a subject in which you are no authority.

I perhaps wouldn't call myself an authority, I still occasionally have to seek more expert advise but after 20 years dealing professionally on an almost daily basis with frame rates and frame rate issues between picture and sound, I would say I've got a fairly decent understanding on the subject.

BTW, in the two different frame rate versions you sent me, I extracted the embedded audio from both and compared them with each other and the separate audio scratch track supplied, most of the time the sync was reasonably close although not perfect but in other places there was up to 4 frames difference between them. This is significant and why changing picture frame rates can be problematic.

G

[PaulGriffith]

Considering the primary edit, CF is right. Dropping 30p footage in a 24p timeline will before fine, in Premiere. Premiere doesn't speed or slow the footage to work, it drops or interpolates frames to keep it the same. Premiere does a fantastic job at it too, I've never been able to see any jitter or resolution loss.

FCP7 is now a 4 or 5 year old program, keep that in mind. It won't handle the difference quite so well. I'm fuzzy on it, but it might not let you put it on the timeline at all, and of it does it'll be render city. Everyone you make a cut or move a clip you'll have to render EVERYTHING. In this case, you can slow the 30p footage down to 24p (and slow down the audio by 20%). What I would try first is converting all your 30p footage to 24p ProRes or something with Compressor. It might drop frames for you and have it looking sharp.

OR... You could download the free 30 day trial of Premiere and finish your edit in a month with way fewer renders and more powerful tools and what not.

[Cracker Funk]

Originally Posted by AudioPostExpert

I'm afraid this is inaccurate, or at least, it is not always accurate. Fractional frame rates, like 23.976fps (or NTSC, 29.97fps) are actually 24fps (or 30fps in the case of NTSC) played slightly slow. One second of time-code with these frame rates does not equal one second of real time, which is why DF (drop frame) rates had to be invented. If you film at 23.976fps (and record audio at this rate) and then do a straight conversion from 23.976fps to 24fps then the picture will slightly speed up relative to the original audio and they will gradually drift out of sync with each other. The way around this is to convert using interpolation but then the issues I listed in my previous post apply. This is true when converting any frame rate to any other frame rate. In fact there is/was a very common workflow which involves this very problem, which is why "pull up" and "pull down" audio recording rates exist.

...

BTW, in the two different frame rate versions you sent me, I extracted the embedded audio from both and compared them with each other and the separate audio scratch track supplied, most of the time the sync was reasonably close although not perfect but in other places there was up to 4 frames difference between them. This is significant and why changing picture frame rates can be problematic.

Right. And that would be expected. Through the entire process, from shooting, to rough cut, everything was shot/edited/exported on/to 23.976. The 1080 version I originally sent you, with timecode, was the first time that true 24p was mistakenly introduced to this project. So, yeah, that would definitely cause sync issues, because it is playing back both video and audio at a slightly slower speed. But had I kept everything in the original 23.976, the shooting frame rate has absolutely no bearing on what is exported.

Regardless, I'm glad you noticed and figured out the problem. Hope it wasn't too big a pain in the rear for you.

I get what you're saying -- frame rate matters. And you pointed out a specific recent example in which frame rate matters. But the frame rate you're talking about is different from the frame rate the OP is asking about. You're talking about the frame rate of the exported rough cut. And that definitely matters. A lot. The OP is asking about the frame rate that the video was shot in, and will be edited in. And that doesn't matter, because by the time it gets to you, it will be conformed to the 23.976, and will match all other footage.

And that is all I meant when I asked whether or not you're an authority on this subject. You're an authority on audio post stuff, no question about that. But that's not the conversation we're having. We're talking about editing video, before it gets to you, and the stuff we're talking about won't effect your job, not ever so slightly.

[Cracker Funk]

Originally Posted by PaulGriffith

OR... You could download the free 30 day trial of Premiere and finish your edit in a month with way fewer renders and more powerful tools and what not.

If I remember correctly, Vegas also handles all formats, in any timeline. So...same idea -- if FCP doesn't work it so well, Vegas would also be an option to download the free trial of. Import all of the footage into a 24p timeline, then export in 24p, and then use all of that converted footage in FCP.

[jax_rox]

I'm pretty sure FCP will handle it, I used to be an FCP buff before I bought Avid.

And I'm not even an editor

The other factor to consider, I would think, is that to assume the audio would be synced later is to assume that the OP has a pro audio post guy lined up. If he doesn't, then there may be an issue here, no?

[chlsy8]

Thanks guys!

I am no tech person. gonna have my editor take a look at this thread...

[AudioPostExpert]

Originally Posted by Cracker Funk

But had I kept everything in the original 23.976, the shooting frame rate has absolutely no bearing on what is exported.

I get what you're saying -- frame rate matters. And you pointed out a specific recent example in which frame rate matters. But the frame rate you're talking about is different from the frame rate the OP is asking about. You're talking about the frame rate of the exported rough cut. And that definitely matters. A lot. The OP is asking about the frame rate that the video was shot in, and will be edited in. And that doesn't matter, because by the time it gets to you, it will be conformed to the 23.976, and will match all other footage.

Ah but it does matter because in audio post we have to deal with all the production sound. So frame rate changes between filming and editing (before audio post) could cause exactly the same problem that we've experienced between editing and audio post. In audio post (whether done by a dedicated audio post guy or the picture editor), you frequently have to go back to the original production sound to find replacement/alternate dialogue, which is going to be a serious problem if the speed of the picture has changed in anyway since the filming because the original production sound will no longer sync with the picture.

With the tried and tested workflow of changing frame rates between filming on 35mm film and editing on video, the speed differences were known and predictable and the production sound mixer would use a pull up sample rate so the production sound could be pulled back down during audio post to sync with the picture edit.

As we have discovered though, when using interpolation in Premiere to convert between frame rates, there are slight discrepancies in picture speed/frame positions, nothing visibly noticeable but enough to cause sync issues with the sound in places. The problem is, that these discrepancies are no longer known or predictable and so cannot be compensated for as could be done with the standard workflow which involved frame rate changes.

Relating this all to the OP's question, he could have problems during dialogue editing when he goes back to the original production sound recorded when the picture was at 30fps.

One last point, Premiere is obviously interpolating both the picture and the linked audio (to maintain sync). Even expensive professional audio tools have difficulty with this type of process without causing some artefacts. You may not notice these artefacts under some conditions but in a cinema, say at a film festival, it's far more likely. It's certainly something I would be concerned about in a professional project.

Originally Posted by Cracker Funk

Regardless, I'm glad you noticed and figured out the problem. Hope it wasn't too big a pain in the rear for you.

It caused a few headaches, half a day or so of extra work and a day or two of delay but it could have been much worse!

G